It is proposed to study two aspects of the visual function of the parietal lobe in waking monkeys using the combined methods of single neuron analysis and behavioral control. Animals are trained in reaction time paradigms that require periods of attentive fixation of small targets, or loci in space at which targets will appear, as the visual properties of parietal light sensitive neurons are explored with other visual stimuli that do not control behavior. We shall study first the effects of the presence of two test stimuli in the field, particularly the spatial interactions between stimuli that vary in size, position, movement, and direction of movement. We shall then change to and experimental paradigm in which the spatial relations between the two stimuli control behavior. In these same paradigms we shall explore further the powerful effects of behavioral state changes upon the sensitivity of parietal neurons to visual stimuli. We shall continue work aimed at developing a multilead microelectrode for recording from large numbers (up to 20) cortical neurons, simultaneously.